KR20090086094A - Systems and methods for detecting the presence of a transmission signal in a wireless channel - Google Patents

Abstract

A method for detecting the presence of a transmission signal in a wireless spectrum channel. The frequency of a signal is converted from a first frequency to a second frequency. The signal with the second frequency is filtered to remove signals that are not within the band of the second frequency. An averaged periodogram of the signal is calculated. A value of the averaged periodogram is compared to a threshold. The presence of the transmission signal is detected, if the value of the averaged periodogram exceeds the threshold. ® KIPO & WIPO 2009

Description

SYSTEM AND METHOD FOR DETECTING THE EXIST OF A TRANSMISSION SIGNAL IN A WIRELESS CHANNEL

Related application

This application is published in US Provisional Application No. 60 / 865,348, filed November 10, 2006 by METHOD AND APPARATUS FOR SPECTRUM SENSING FOR WIRELESS COMMUNICATION by inventor Stephen J. Shellhammer. The priority is given to the provisional application, which is hereby incorporated by reference.

Field of technology

The present invention relates generally to telecommunications and wireless communication-related technologies. More particularly, the present invention relates to a system and method for detecting the presence of a transmission signal in a wireless channel.

background

Wireless communication networks are widely deployed to provide various types of services such as voice, packet data, broadcast, and the like. For example, these wireless networks may include code division multiple access 2000 (CDMA2000) networks, global system for mobile communications (GSM) networks, wideband code division multiple access (W-CDMA) networks, and WiMAX (Wide Interoperability for Microwave). Access) network.

Each wireless network uses a specific air interface to support air-over-the-air communication, and typically additionally implements a specific mobile networking protocol that supports roaming and advanced services. For example, W-CDMA networks utilize code division multiple access (CDMA) air interfaces and GSM EDGE Radio Access Network (GERAN) networking protocols.

The telecommunication standards described above are examples of some of the various communication systems that may be implemented for transmitting voice and / or data. Within these systems, multiple channels may be available for use by multiple types of transmissions. Devices in these systems may scan the frequency spectrum of these channels for the purpose of identifying unused spectrum, but certain types of transmissions using the frequency spectrum may not be detected. As such, advantages may be realized by improved systems and methods for detecting the presence of a transmission signal in a wireless channel.

Brief description of the drawings

1 illustrates a network configuration in accordance with an example of the systems and methods of the present invention.

2 is a block diagram illustrating another example of a user device.

3 is a flowchart illustrating an example of a method for determining whether a channel is occupied by an authorized transmission.

3A shows means plus functional blocks corresponding to the method shown in FIG. 3.

4 is an example of a process illustrating the conversion of a first frequency signal to a second frequency signal.

5 is an example of a process illustrating the conversion of a second frequency signal into a complex baseband signal.

6 is another example of a process illustrating the conversion of a second frequency signal into a complex baseband signal.

7 is a process illustrating an example of calculating an averaged periodogram.

8 illustrates various components that may be used in a wireless device.

details

A method for detecting the presence of a transmission signal in a radio spectrum channel is described. The frequency of the signal is converted from the first frequency to the second frequency. The signal of the second frequency is filtered to remove signals that are not in the band of the second frequency. The averaged periodogram of the signal is calculated. The value of the averaged periodogram is compared with the threshold. If the value of the averaged periodogram exceeds the threshold, the presence of the transmission signal is detected.

Also described is a wireless device for detecting the presence of a transmission signal in a radio spectrum channel. The wireless device includes a processor and memory in electronic communication with the processor. The instructions are stored in that memory. The frequency of the signal is converted from the first frequency to the second frequency. The signal at that second frequency is filtered to remove signals that are not in the band of that second frequency. The averaged periodogram of the signal is calculated. The value of the averaged periodogram is compared with the threshold. If the value of the averaged periodogram exceeds the threshold, the presence of the transmission signal is detected.

Also described is an apparatus configured to detect the presence of a transmission signal in a radio spectrum channel. The apparatus includes means for converting the frequency of the signal from the first frequency to the second frequency, and means for filtering the signal at the second frequency to remove signals that are not in the band of the second frequency. The apparatus also includes means for calculating an averaged periodicity of the signal. The apparatus further includes means for comparing the value of the averaged periodogram with a threshold, and means for detecting the presence of a transmission signal if the averaged periodogram exceeds the threshold.

Also described is a computer-program product for detecting the presence of a transmission signal in a radio spectrum channel. The computer-program product includes a computer readable medium having instructions. The instructions include code for converting a frequency of the signal from a first frequency to a second frequency, and code for filtering a signal of that second frequency to remove signals that are not in the band of the second frequency. do. The instructions also include code for calculating the averaged periodogram of the signal. The instructions further include code for comparing the value of the averaged periodogram with a threshold, and code for detecting the presence of a transmission signal if the value of the averaged periodogram exceeds a threshold.

Cognitive radio scans the RF spectrum for the purpose of identifying unused frequency bands within a radio frequency (RF) spectrum. Unused frequency bands may be used for unauthorized wireless operation. Hereinafter, the process of scanning the RF spectrum to identify unused frequency bands may be referred to as “spectrum sensing”. In some examples, unused television (TV) channels within a particular geographic range are used for unauthorized cognitive radio operation. Hereinafter, these unused TV channels are often referred to as "whitespace".

The Institute of Electrical and Electronic Engineer (IEEE) has formed a working group (ie IEEE 802.22) to develop a standard for wireless local area networks (WRAN) operating on these geographically unused TV channels. The IEEE standard includes cognitive radio technologies for the identification of these unused TV channels. There are several possible authorized transmissions that may occupy a TV channel. Specific examples of these transmissions include analog TV, Advanced Television Systems Association (ATSC) digital TV, professional wireless microphones, and the like. In one example, if the authorized transmission is above a certain power threshold, the TV channel is considered to be occupied, otherwise the TV channel is considered not occupied and thus available for unauthorized wireless use. The systems and methods of the present invention describe a method of identifying TV channels not occupied by ATSC television transmission.

Cognitive radio has the ability to scan the spectrum and detect the presence of a signal from an authorized transmission. Cognitive radio detects the presence of a signal with a low signal-to-noise ratio (SNR). This is because cognitive radio may be in a faded location and still be able to detect authorized transmissions. The IEEE 802.22 WRAN includes a sensing condition that allows a signal from an ATSC transmission (hereafter referred to as an "ATSC signal") to be detected at -116 dBm corresponding to about -21 decibel (dB) SNR. Thus, the ATSC signal is 21 dB weaker than the noise level.

The ATSC signal includes some characteristics that cognitive radio may use to detect weak ATSC signals. One of these characteristics includes a sinusoidal pilot signal. This pilot signal is 11.3 dB weaker than the data portion of the ATSC signal. Conventional systems and methods suggest filtering the frequency of a pilot signal with a 10 kilohertz (KHz) filter, and then using the resulting signal power to detect the presence of an ATSC signal, but such an approach is provided above. It does not meet the detection conditions of IEEE 802.22. The system and method of the present invention describe a method for determining which TV channels are occupied by an authorized transmission, such as an ATSC transmission, wherein the SNR is less than -21 dB SNR, which is defined as a condition by the IEEE 802.22 working group. Much lower.

1 illustrates a network configuration 100 in accordance with an example of the system and method of the present invention. Configuration 100 includes a plurality of base stations 110, 112, 114, 116, 118 and a plurality of user devices 108A-108K. User devices 108A-108K may be cognitive wireless device, wireless device, mobile station, or the like. Configuration 100 also includes a plurality of service areas 150, 152, 154, 156, 158. The first service area 150 includes a first base station 110 and a plurality of user devices 108A-108K. The first service area 150 may overlap the second service area 152, the third service area 154, the fourth service area 156, and the fifth service area 158. As shown, some user devices may be located in service areas overlapped by different service areas.

The plurality of base stations 110, 112, 114, 116, 118 may provide service to user devices located in their respective service area. For example, the first base station 110 may provide services to, and perform communications with, user devices located in the first service area 150. Each of the plurality of user devices 108A-108K can scan a band of frequencies used by other user devices as well as frequencies used by one or more base stations 110, 112, 114, 116, 118. It may be. A user device located in an overlapping area between two service areas may scan the frequency band used by each base station providing a service in that overlapping area. In addition, each of the user devices may sense whether the channel is occupied by an authorized transmission. For example, each user device may detect whether a TV channel is currently occupied by an authorized ATSC transmission. Unoccupied channels may be used for unauthorized wireless operation by user devices 108A-108K.

In one example, the ATSC signal occupies a 6 megahertz (MHz) TV channel. The TV channel may range from 54 MHz in the low very high frequency (VHF) band to 698 MHz in the ultra high frequency (UHF) band. The sinusoidal pilot signal may be inserted into the ATSC baseband signal prior to conversion of the ATSC baseband signal to a radio frequency (RF) signal and transmission of the ATSC baseband signal. The frequency of the pilot signal may be specified for the edge of the lower band of the TV channel used. There may be a number of different pilot frequencies that may be used. In one example, the exact pilot frequency is determined by external conditions. For example, the exact pilot frequency may be determined based on other TV signals present in the same geographic area. Two possible pilot frequencies may be as follows.

2 is a block diagram illustrating another example of a user device 208. The user device 208 may be cognitive radio, radio station, user equipment (UE), or the like. The frequency converter 202 may convert the received RF signal into an intermediate frequency (IF) signal by mixing the sinusoidal local oscillator and the received RF signal. For the lower band edge of the 6 MHz IF band, the pilot frequency of the received signal after conversion to IF is the same value used for transmission, but any error in the receiver local oscillator (LO) frequency is unknown at the pilot frequency. May result in a shift. If the LO is accurate within ± δ ppm (parts per million) and the LO frequency is f _0, then the LO frequency error may be given by

The LO frequency f ₀ may be the difference between the RF frequency and the IF frequency. For an ATSC signal, the LO frequency f ₀ may be less than 700 MHz. Thus, the worst case LO frequency error may be as follows.

As a result of the LO frequency error, the pilot frequency f _p at IF (and subsequently baseband) is in the range between:

For a very accurate LO with 2 ppm accuracy (δ = 2), the pilot frequency f _p is in the following range.

Thus, there is approximately pilot frequency uncertainty in the IF as follows.

The frequency of the pilot signal inserted into the ATSC signal should be a frequency that includes a bandwidth greater than the pilot frequency uncertainty provided by equation (5).

The signal filter 204 may be used to filter any out-of-band signals from the converted frequency signal. In one example, signal converter 206 converts the IF signal into a complex signal. The resulting complex signal may be filtered by signal filter 204 to capture the ATSC pilot signal. The periodogram generator 208 may be used to generate an averaged periodogram. The power spectrum estimator 210 may estimate the power spectrum of the complex signal using its averaged periodogram. The test statistics comparator 212 may compare the value of the averaged periodogram with a predetermined threshold. If the value of the averaged periodogram exceeds a threshold, it may be determined that the ATSC signal is present on a particular TV channel. That is, it may be determined that a particular TV channel is already occupied by an authorized transmission.

3 is a flow diagram illustrating an example of a method 300 for determining whether a channel is occupied by an authorized transmission. In one example, the channel is a TV channel and the authorized transmission is an ATSC transmission. The frequency of the signal may be converted from the first frequency to the second frequency (302). For example, the RF signal may be converted to an IF signal. The signal may be converted 302 using a local oscillator (LO) and an RF mixer. The signal of the second frequency may be filtered (304). In one example, the IF signal is filtered 304 to remove out-of-band signals. The signal of the second frequency may be converted to a complex baseband signal (306). In addition, the complex baseband signal may be filtered. In one example, the averaged periodogram of the complex baseband signal is calculated (308). Further, based on the averaged periodogram, an estimate of the power spectrum of the complex baseband signal is calculated. The averaged periodicity may be compared 310 with a threshold. The results of comparison 310 determine whether the channel is occupied or not occupied by an authorized transmission.

The method of FIG. 3 described above may be performed by various hardware and / or software component (s) and / or module (s) corresponding to the means-plus-function blocks shown in FIG. 3A. That is, the blocks 302A through 310A shown in FIG. 3A correspond to the means-plus-blocks 302 through 310 shown in FIG. 3.

일 수도 있으며, 여기서, 로컬 오실레이터 (408) 의 주파수 f_LO1 는 제 1 주파수와 제 2 주파수 (즉, RF와 IF) 사이의 차이이다. 필터링되지 않은 제 2 주파수 신호가 신호 필터 (404) 에 의해 필터링되어, 제 2 주파수 신호 (410) 를 생성할 수도 있다. 신호 필터 (404) 는, 임의의 대역-외 신호들을 필터링하는 6MHz IF 기저대역 필터일 수도 있다.4 is an example of process 400 illustrating the conversion of first frequency 402 to second frequency 410. The first frequency signal 402 may be an RF signal and is provided to the mixer 406 (such as an RF mixer). The first frequency signal 402 may be mixed with a sinusoidal signal provided by the local oscillator 408. Sine wave signal ho

It may be, where the frequency f _LO1 of the local oscillator 408 is the difference between the first frequency and the second frequency (ie, RF and IF). The unfiltered second frequency signal may be filtered by signal filter 404 to generate second frequency signal 410. Signal filter 404 may be a 6 MHz IF baseband filter that filters any out-of-band signals.

일 수도 있다. 또한, 제 2 주파수 신호 (510) 는, 제 2 로컬 오실레이터 (508B) 로부터의 정현파 신호와 믹싱되기 위해 제 2 믹서 (506B) 로 전송될 수도 있다. 제 2 로컬 오실레이터 (508B) 로부터의 정현파 신호는

일 수도 있다.5 is an example of process 500 illustrating the conversion of a second frequency signal 510 to a complex baseband signal 514, 516. Process 500 may implement low speech analog-to-digital conversion (ADC) and analog filtering. The second frequency signal 510 may be sent to the first mixer 506A for mixing with a sinusoidal signal from the first local oscillator 508A. The sinusoidal signal from the first local oscillator

It may be. The second frequency signal 510 may also be sent to the second mixer 506B for mixing with a sinusoidal signal from the second local oscillator 508B. The sinusoidal signal from the second local oscillator 508B

It may be.

The following provides an example of a process for determining the frequency f _LO2 . In one example, the frequency midway between two possible ATSC pilot frequencies (shown in Table 1 above) is converted to the frequency of a direct current (DC) signal. The DC signal is at frequency f = 0. The frequency intermediate between two ATSC pilot frequencies is provided by

The IF frequency f _IF may be specified. An example of an IF frequency may be 5.38 MHz, but another IF frequency may be specified. As mentioned above, the ATSC pilot is referenced from the lower band edge of the 6 MHz TV channel. Based on the frequency intermediate and the IF frequency f _IF calculated from Equation 6, the frequencies of the local oscillators 508A, 508B for conversion from the IF signal to the complex baseband signal are as follows.

The unfiltered mixed signal is filtered by signal analog filters 504A, 504B with a low pass filter having a bandwidth wide enough to capture the ATSC pilot signal. Hereinafter, the bandwidth of the low pass analog filter may be referred to as "BW". In one example, the actual BW is chosen to be wider than the pilot frequency uncertainty described above in equation (5). The filtered complex signal may be sampled with an analog-to-digital converter (ADC) 512A, 512B at a sample rate of at least BW Hz. In some examples, the sample rate is greater than the BW. The in-phase component 514 of the complex signal and the quadrature component 516 of the complex signal may be the output of the process 500.

6 is another example of a process 600 illustrating the conversion of a second frequency signal 610 into a complex baseband signal 620, 622. In contrast to the process 500 described in FIG. 5, the process 600 shown in FIG. 6 may implement high speed ADC and digital filtering. Since the same circuit may be used to sense an authorized transmission (eg, an ATSC transmission), the process 600 may be used when a high speed analog-to-digital conversion is implemented to detect other major signals.

를 포함할 수도 있다. 또한, 제 2 주파수 신호 (610) 는, 제 2 로컬 오실레이터 (608B) 로부터의 정현파 신호와 믹싱되도록 제 2 믹서 (606B) 에 전송될 수도 있다. 제 2 로컬 오실레이터 (608B) 로부터의 정현파 신호는

일 수도 있다. 제 2 주파수 신호 (610) 가 복소 아날로그 기저대역 신호로 변환될 수도 있으며, 6MHz ATSC 신호는 DC의 중앙에 위치된다. 따라서, 제 1 및 제 2 로컬 오실레이터 (608A, 608B) 의 주파수 f_LO3 는 다음에 의해 제공되는 바와 같은 IF 주파수일 수도 있다.The second frequency signal 610 may be provided to the first mixer 606A to be mixed with the sinusoidal signal from the first oscillator 608A. The sinusoidal signal from the first local oscillator 608A

It may also include. The second frequency signal 610 may also be sent to the second mixer 606B to be mixed with the sinusoidal signal from the second local oscillator 608B. The sinusoidal signal from the second local oscillator 608B

It may be. The second frequency signal 610 may be converted to a complex analog baseband signal, with the 6 MHz ATSC signal located at the center of the DC. Thus, the frequencies f _LO3 of the first and second local oscillators 608A, 608B may be IF frequencies, as provided by the following.

The mixed unfiltered signal may be sent to signal analog filters 604A, 604B to be filtered with a low pass filter, and sampled by ADCs 612A, 612B at a sampling rate fs of at least 6 MHz. The complex signals 614, 616 may be digitally frequency converted such that the frequency intermediate between the possible ATSC pilot frequencies is DC.

일 수도 있다. 복소 신호의 직교위상 컴포넌트 (616) 는, 제 4 로컬 오실레이터 (608D) 로부터의 정현파 신호와 믹싱되도록 제 2 믹서 (606D) 에 전송된다. 제 4 로컬 오실레이터 (608D) 로부터의 정현파 신호는

일 수도 있다. 가능한 ATSC 파일럿 주파수들 사이의 주파수 중간을 변환하는 디지털적인 주파수 변환을 위한 제 3 로컬 오실레이터 (608C) 및 제 4 로컬 오실레이터 (608D) 의 주파수 f_LO4 는 다음에 의해 주어질 수도 있다.The in-phase component 614 of the complex signal is sent to the first mixer 606C to mix with the sinusoidal signal from the third local oscillator 608C. The sinusoidal signal from the third local oscillator 608C

It may be. The quadrature component 616 of the complex signal is sent to the second mixer 606D to be mixed with the sinusoidal signal from the fourth local oscillator 608D. The sinusoidal signal from the fourth local oscillator 608D

It may be. The frequency f _LO4 of the third local oscillator 608C and the fourth local oscillator 608D for digital frequency conversion that converts the frequency intermediate between possible ATSC pilot frequencies may be given by:

Since this frequency conversion is performed in the digital domain, the analog frequency f _LO4 is converted into the digital domain by dividing that f _LO4 by the sampling rate f _s .

The analog-filtered signal is sent to the first decimation phase 620A and the second decimation phase 620B. The decimation phases 620A, 620B include digital signal filters 604C, 604D that filter the analog-filtered signal with a low pass filter of BW bandwidth. The bandwidth of the digital signal filter may be referred to as DBW. The BW may even be large enough to capture an ATSC pilot with the pilot frequency uncertainty provided in equation (5). The DBW of the digital signal filters 604C, 604D may be a BW divided by the sampling rate f _s .

The digitally-filtered signal may be sent to down sampler 618A, 618B that downsamples the signal at the next rate.

In some examples, the sampling rate is 6 MHz and the digital filter 604C, 604D DBW is about 25 KHz. Thus, the down sampling rate M is approximately a factor of 240. As described above, low pass filtering by the digital filters 604C, 604D and down sampling of the signal may be referred to as decimation. The outputs 620, 622 of the first and second decimation phases 620A, 620B may be digital complex baseband signals 620, 622.

7 is a process 700 illustrating an example of calculating an averaged periodogram 712. The digital complex baseband signal 724 may be provided to the serial-to-parallel converter 702. In one example, the periodogram of the digital complex baseband signal 724 is given by

The argument of the sum may be a Discrete Fourier Transform (DFT), which may be implemented by the Fast Fourier Transform component 704 using a Fast Fourier Transform (FFT). The absolute value component 706 provides the absolute value of the FFT, with each output of that FFT squared. The summing component adds together the samples taken from the signal 724. The repeating component 710 obtains additional samples from the signal 724 until a predetermined number of samples are obtained. For example, baseband signal 724 is observed for multiple time segments. In each time segment, N samples are obtained. In one example, M time segments are used. These M time segments do not need to be contiguous in time. For example, these time segments M may occur periodically.

In some instances, network transmission is stopped during the sensing time to best observe the spectrum during the sensing time. Hereinafter, the sensing time at which network transmission is stopped may be referred to as a "quiet time". Since the sensing intervals do not need to be contiguous in time, it is possible to space the sensing intervals so that the total idle time is subdivided into a series of shorter idle times. Since network transmissions are paused for idle time, it may be desirable to minimize the duration of each sensing interval. This may result in less impact on network latency. For example, if the network is using a conventional frame structure, the sensing time may be subdivided into M sensing intervals. Each sensing interval may be the length of a single frame, and each sensing interval may be separated by multiple frames. In one example, the effect of downtime on network latency is during a single frame.

The periodogram may be calculated for each sensing interval. Thus, according to the above example, there are M period diagrams, one from each sensing interval. The systems and methods of the present invention may use an averaged periodogram 712. The averaged periodogram 712 may be the sum of each of the individual periodograms from each sensing interval, divided by the number of sensing intervals. The summation may be performed by the summation component 708. An example of an averaged periodogram 712 is provided by:

In Equation 12, P _m (ω) may be a periodogram from the Mth sensing interval at the angular frequency ω. If M is fixed, there is no need to divide by M. The threshold at which the averaged periodogram 712 is compared may be scaled to M. Eliminating division with M simplifies the complexity of the systems and methods of the present invention.

After calculating the periodogram for each sensing interval, the largest value of the averaged periodogram 712 may be selected as the test statistics. The test statistics may be provided as follows.

The determination of whether the ATSC signal is present in the TV channel is determined by whether the test statistics from Equation 13 exceed a predetermined threshold. This determination may be expressed as follows.

If the test statistic T exceeds the threshold c ₁ , a decision D ₁ may be selected indicating that the ATSC signal is present on the TV channel. On the other hand, if the test statistics do not exceed the threshold, a decision D ₀ may be selected indicating that the ATSC signal is not present on the TV channel.

In another example, a final check may be made to ensure that the test statistics do not exceed the threshold due to interference from another wireless system. Further, in addition to comparing the test statistic T with a predetermined threshold c ₁ , a second threshold, which is a function of the data, may be calculated. If the test statistics exceed the second threshold, a determination may be made as to whether the determination using the threshold c ₁ was due to false detection.

In one example, the N values of the averaged periodogram 712 may be labeled with a vector P, the entries of which are provided as follows.

To select a second threshold that depends on data, one or more of the N values may be zeroed out near the frequency of the maximum of the N values. The index of the vector P that provides the maximum of N values may be m. This index may also be a test statistic that

In one example, the values of P near index m may be zeroed out. The new vector may be given by

That is, when the maximum value of the periodogram is located, 2k + 1 values of the periodogram located at the center are zeroed out. The second threshold dependent on the data may be a scaled version of the maximum of periodogram values that have not been zeroed out. The second threshold may be provided as follows.

In one example, the value of α is selected to make an adjustment between the false alarm rate and the detection probability. In implementing these two thresholds, the determination that the ATSC signal is present in the TV channel occurs when the test statistics exceed the maximum of the two thresholds c ₁ and c ₂ .

8 illustrates various components that may be used in the wireless device 802. The wireless device 802 is an example of a device that may be configured to implement the various methods described herein. The wireless device 802 may be a base station 110, 112, 114, 116, 118 or user device 108A-108K.

The wireless device 802 may include a processor 804 that controls the operation of the wireless device 802. In addition, the processor 804 may be referred to as a central processing unit (CPU). Memory 806, which may include both read-only memory (ROM) and random access memory (RAM), provides instructions and data to the processor 804. Also, part of the memory 806 may include non-volatile random access memory (NVRAM). Typically, processor 804 performs logic and arithmetic operations based on program instructions stored in memory 806. The instructions in the memory 806 may be executable to implement the methods described herein.

In addition, the wireless device 802 may include a housing 808, which may include a transmitter 810 and a receiver 812 that allow transmission and reception of data between the wireless device 802 and a remote location. . The transmitter 810 and receiver 812 may be combined into a transceiver 814. Antenna 816 may be attached to housing 808 and may be electrically coupled to transceiver 814. In addition, the wireless device 802 may include multiple transmitters, multiple receivers, multiple transceivers, and / or multiple antennas (not shown).

In addition, the wireless device 802 may include a signal detector 818, which may be used to detect and quantify the level of signals received by the transceiver 814. The signal detector 818 may detect total energy, pilot energy per pseudonoise (PN) chips, signals such as power spectral density, and other signals. In addition, the wireless device 802 may include a digital signal processor (DSP) 820 for use in processing signals.

The various components of the wireless device 802 may be coupled together by a bus system 822, which may include a power bus, a control signal bus, and a status signal bus, in addition to a data bus. However, for clarity, various buses are shown in FIG. 8 as bus system 822.

As used herein, the term "determining" (and its grammatical variations) is used in a very broad sense. The term "determining" encompasses a wide variety of actions, and thus "determining" means calculating, calculating, processing, deriving, investigating, looking up (e.g., a table, a database or Look up on other data structures), verify, and the like. In addition, “determining” may include receiving (eg, receiving information), accessing (eg, accessing data in a memory), and the like. Also, “determining” can include resolving, selecting, choosing, establishing, and the like.

Information and signals may be represented using a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, etc., which may be referenced throughout the above description, may be represented by voltage, current, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. It may be.

The various illustrative logic blocks, modules, and circuits described in connection with the present disclosure are general purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays designed to perform the functions described herein. It may be implemented or performed in a signal (FPGA) or other programmable logic device, separate gate or transistor logic, separate hardware components, or any combination thereof. A general purpose processor may be a microprocessor, but in other ways, the processor may be any commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, eg, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of the method or algorithm described in connection with the present invention may be embodied directly in hardware, in a software module executed by a processor, or in a combination of both. The software module may reside in any form of storage medium known in the art. Some examples of storage media that may be used include RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs, and the like. A software module may include a single instruction or a plurality of instructions and may be distributed over several different code segments, among different programs, and across multiple storage media. The storage medium may be coupled to the processor such that the processor can read information from and write information to the storage medium. In the alternative, the storage medium may be integral to the processor.

The methods disclosed herein comprise one or more steps or actions for achieving the described method. Method steps and / or actions may be interchanged with one another without departing from the scope of the claims. That is, unless a specific order of steps or actions is specified, the order and / or use of specific steps and / or actions may be modified without departing from the scope of the claims.

디스크를 포함하며, 디스크 (disk) 들은 일반적으로 데이터를 자기적으로 재생하지만, 디스크 (disc) 들은 레이저에 의해 광학적으로 데이터를 재생한다.The functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions on a computer-readable medium. A storage medium may be any available medium that can be accessed by a computer. By way of example, and not limitation, such computer-readable media may comprise desired program code in the form of RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage device, or instruction or data structure. May be used to carry or store the device, and may include any other medium that can be accessed by a computer. As used herein, discs and discs include compact discs, laser discs, optical discs, digital versatile discs, floppy discs, and Blu-ray discs.

Including disks, disks generally reproduce data magnetically, while disks optically reproduce data by laser.

In addition, the software or instructions may be transmitted via a transmission medium. For example, software transmits from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, wireless, and microwave If so, coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, wireless and microwave are included in the definition of transmission medium.

It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes, and variations may be made to the arrangement, operation and details of the above-described methods and apparatus without departing from the scope of the claims.

Claims (22)

A method for detecting the presence of a transmission signal in a radio spectral channel, Converting the frequency of the signal from the first frequency to the second frequency; Filtering the signal of the second frequency to remove signals that are not in the band of the second frequency; Calculating an averaged periodogram of the signal; Comparing the averaged periodogram value with a threshold value; And Detecting the presence of the transmitted signal if the value of the averaged periodogram exceeds the threshold. The method of claim 1, Determining the maximum value of the averaged periodogram. The method of claim 2, And comparing the maximum value of the averaged periodogram with the threshold value. The method of claim 1, Wherein the frequency of the signal is a radio frequency. The method of claim 1, And converting said signal into a complex digital signal. The method of claim 5, wherein Estimating a power spectrum of the complex digital signal using the averaged periodogram. The method of claim 1, And comparing the value of the averaged periodogram with a data dependent threshold. The method of claim 7, wherein If the value of the averaged periodogram exceeds the threshold and the data dependent threshold, detecting the presence of the transmission signal. The method of claim 1, And wherein said radio spectrum channel is a television (TV) channel. The method of claim 1, Detecting the presence of the transmitted signal is implemented by a cognitive radio device. The method of claim 1, And wherein said transmit signal is an Advanced Television System Association (ATSC) signal. A wireless device for detecting the presence of a transmission signal in a wireless spectral channel, A processor; Memory in electronic communication with the processor; And Instructions stored in the memory, The instructions are Convert a frequency of the signal from the first frequency to the second frequency; Filtering the signal of the second frequency to remove signals that are not in the band of the second frequency; Calculate an averaged periodogram of the signal; Compare the value of the averaged periodogram with a threshold; And, And if the value of the averaged periodogram exceeds the threshold, executable to detect the presence of the transmitted signal. The method of claim 12, The wireless device is a handset. The method of claim 12, The wireless device is a base station. The method of claim 12, The instructions are further executable to determine a maximum value of the averaged periodogram. The method of claim 15, The instructions are further executable to compare the maximum value of the averaged periodogram with the threshold. The method of claim 12, And the frequency of the signal is a radio frequency. The method of claim 12, The instructions are further executable to convert the signal into a complex digital signal. The method of claim 18, And the instructions are further executable to estimate a power spectrum of the complex digital signal using the averaged periodogram. The method of claim 12, And the transmit signal is an Advanced Television System Association (ATSC) signal. An apparatus configured to detect the presence of a transmission signal in a radio spectrum channel, the apparatus comprising: Means for converting a frequency of the signal from the first frequency to the second frequency; Means for filtering the signal at the second frequency to remove signals that are not in the band at the second frequency; Means for calculating an averaged periodogram of the signal; Means for comparing the value of the averaged periodogram with a threshold; And Means for detecting the presence of the transmission signal if the value of the averaged periodogram exceeds the threshold. A computer-program product comprising a computer readable medium having instructions for detecting the presence of a transmission signal in a radio spectrum channel, the method comprising: The instructions are Code for converting a frequency of a signal from a first frequency to a second frequency; Code for filtering the signal of the second frequency to remove signals that are not in the band of the second frequency; Code for calculating an averaged periodogram of the signal; Code for comparing the value of the averaged periodogram with a threshold; And And code for detecting the presence of the transmitted signal if the value of the averaged periodogram exceeds the threshold.

Images